This invention relates to a process for producing diaminomaleonitrile, tetramer of hydrogen cyanide. Diaminomaleonitrile is a useful chemical product which is used as a raw material in the chemical industry for various organic materials, especially as an intermediate for synthesis of glycine, guanine, ademine, 4-aminoimidazole-5-carboxamide or the like.
German Disclosure Patent No. 2022243 discloses a process for producing diaminomaleonitrile wherein hydrogen cyanide is polymerized in a polar aprotic solvent, i.e. dimethyl sulfoxide and dimethyl formamide, in the presence of a basic catalyst such as NaCN, KCN, NaOH and (C.sub.2 H.sub.5).sub.3 N, maintaining the reaction mixture at a PH value of 10.+-.1, and thereby diaminomaleonitrile is obtained with a yield of 37 to 64%.
According to Japanese Disclosure Patent No. 2917/1971, diaminomaleonitrile is obtained with a yield of 16 to 63%, by polymerizing hydrogen cyanide at a temperature ranging from about -40.degree.C to 25.degree.C in the presence of a basic catalyst such as trimethylamine, and at least one cocatalyst selected from the group consisting of dicyan and diiminosuccinonitrile.
According to Japanese Disclosure Patent No. 64021/1973, diaminomaleonitrile is obtained with a yield of 41 to 55.7% by polymerizing hydrogen cyanide employing saturated aliphatic mononitrile as a solvent in the presence of a basic catalyst.
The above-mentioned processes produce the desired compound with a low yield, so that the said compound, i.e. diaminomaleonitrile is expensive and useful chemicals such as glycine, guanine, ademine and 4-aminoimidazole-5-carboxamide which are synthesized from the said diaminomaleonitrile are also expensive. Consequently, those processes are economically unattractive.
A condition for producing diaminomaleonitrile from hydrogen cyanide with a high yield is to accelerate the velocity of converting hydrogen cyanide into diaminomaleonitrile and simultaneously to control the secondary reaction converting hydrogen cyanide into a high polymer.
The inventors scrutinized those conventional economically poor processes for producing diaminomaleonitrile and carried out the various types of research so as to find a method for improving those drawbacks.
As a result of the research, the inventors found that diaminomaleonitrile is obtained with a surprising high yield in a short reaction time by using organic mercaptans or organic disulfides as a catalyst when carrying out the polymerization reaction of hydrogen cyanide in a solvent in the presence of a basic catalyst.
It is the object of the invention to overcome the aforementioned problems and disadvantages and provide an improved process for producing diaminomaleonitrile.
Other and further objects, features and advantages of the invention will appear more fully from the following description.